Quasi-Thermal Noise in Space Plasma with "Kappa" Distributions : first results

The transport of the energy in space plasma, especially in the solar wind,is far from being understood. Measuring the temperature of the electrons and their non thermal properties must give important clues to understand the transport properties. Quasi-thermal noise spectroscopy is a reliable tool for measuring accurately the electron temperature since it is less sensitive to the spacecraft perturbations than particle detectors. We model the Quasi-Thermal Noise (QTN) with a generalized Lorentzian ("Kappa") distribution function defined by three parameters : the electron density, temperature and kappa index. For collisionless and drifting plasma (like the solar wind), this noise is produced by the quasi-thermal fluctuations of the electrons and by the Doppler-shifted thermal fluctuations of the ions. We explain the calculations to real values of κ and give the analytic expressions and numerical calculations of the QTN with "kappa" distribution function. We also show some generic properties of the QTN. We apply this method to Ulysses/URAP data, as this probe flew by pole-to-pole during more than a solar activity cycle. We compare these new results to those obtained from the same data set but assuming a classical core + halo distribution. These results will allow us to discuss the variations with heliocentric distance and latitude of the 3-fitted parameters : the electron density, temperature and kappa index of the distribution. Especially, the total temperature variation with distance during the solar minimum at high latitudes will be compare with the temperature profile predicted by a kinetic collisionless model of the solar wind.